Spinneret



A. L. BREEN Dec. 26, 1961 SPINNERET 2 Sheets-Sheet 1 Filed March 25,1957 g. I

INVENTOR ALVIN L. BREEN A. L. BREEN Dec. 26, 1961 SPI'NNERET 2Sheets-Sheet 2 Filed March 25, 1957 INVENTOR ALVIN L. BREEN I BY GZMATTORNEY United States 3,ti14,237 SFINNERET Alvin L. Breen, WestChester, Pa., assignor to E. I. do Font de Nemours and Company,Wilmington, Del., a corporation of Delaware Filed Mar. 25, 1957, Ser.No. 648,420 2 Claims. (Cl. 188) This invention relates to a novelspinneret for the production of filaments.

There have been various types of spinnerets proposed for the spinning ofhollowand also of composite filaments. Such spinnerets are adaptedeither to the production of hollow filaments or of composite filaments,but not of both, and have the further disadvantage of complexity, highcost, inefiectiveness in the production of uniform filaments ofpredetermined cross-section and lack of flexibility in the production offilaments over a wide range of denier. Also, many of these spinneretsare not adapted to produce filaments of which the components are, incross-section, eccentrically disposed with respect to each other, adesideratum for the production of inherently crimpable or crimpedfilaments. There is a need for a design of spinneret which, in part orin whole, overcomes these and similar deficiencies.

It is an object of this invention to provide a new type of spinneret. Itis a further object of this invention to provide novel spinnerets forthe production of hollow and composite filaments, particularly thosecomposed in whole or in part of synthetic linear polymers. An additionalobject is the provision of a new type of spinneret adaptable for themelt-spinning of filaments.

The objects of this invention have been attained by providing aspinneret in the spinning orifices of which is positioned a hollow pinconnected to a source of fluid supply for extruding, simultaneously witha fiber-forming polymer, a gas, another polymer which may befiber-forming, a molten metal or other liquid material. Such a spinneretis suitable for the production of hollow filaments and of compositefilaments of various types.

Although the spinneret of this invention may be applied to the spinningof any forms of composite filaments, the following description andexamples will, for purposes of illustration, be largely directed to theproduction of hollow filaments by the melt-spinning process.

In the drawings:

FIGURE 1 is a top plan View of the upper plate or filter pack of aspinneret used in the practice of this invention;

FIGURE 1(a) is an elevation view in cross-section of the upper plate orfilter pack taken along the lines 1llll of FIGURE 1. The right-hand halfof FIGURE 1(a) is an elevation in cross-section along the plane of theright-hand half of line 1a1a of FIGURE 1 and the lefthand half of FIGURE1(a) is an elevation in cross-section along the plane of the left-handhalf of line Ia1a of FIGURE 1. It will be noted that the two portions ofline 1a1a of FIGURE 1 form an angle at the center of the figure. The twohalves of FIGURE 1(a) have been assembled in this fashion in order toshow the shape and direction of the different holes and cavities eventhough they may not fall along the central plane of the spinneret;

FIGURE 2 is a bottom plan view of the apparatus of FIGURE 1 taken at asomewhat different angle than FIGURE 1, line 1a1a of FIGURE 2 likewiseshowing the dual plane cut of FIGURE 1(a);

FIGURE 3 is a top plan view of the bottom plate of a spinneret used inthe practice of this invention;

FIGURE 4 is an elevation View in cross-section of the bottom spinneretplate shown in FIGURE 3 with the right-hand half shown in the plane ofthe right-hand half of line 4-4 of FIGURE 3 (drawn to the center) andwith ice the left-hand half of FIGURE 4 being cut on the plane of thevertical portion (from the center downwardly) of line 44 of FIGURE 3. Asin the case of FIGURE 1(a), FIGURE 4 is assembled in the mannerindicated to show the shape and direction of the holes and otherelements of the bottom spinneret plate although, as is evident fromFIGURE 3, these elements are not, in fact, aligned as shown in FIGURE 4;

FIGURE 5 is an elevation view, generally in crosssection, of the upperand lower plates of FIGURES 1, 1(a), 2, 3 and 4, in assembled positionutilizing the showing of FIGURE 4 for the lower plate and the showing ofco-acting parts of FIGURES 1, 1(a) and 2 for the upper plate or filterpack. FIGURE 5 shows the assembled spinneret with a full showing of thevarious elements, with the upper plate being shown, as assembled, in theposition corresponding to that of the lower plate;

FIGURE 6 is an elevation (magnified and paitly in section) of theextrusion pin shown in'FIGURE 5;

FIGURE 7 is a cross-section taken on 7-7 of FIG- URE 6;

FIGURE 8 is a cross-section taken on line 88 of FIGURE 6;

FIGURE 9 is a cross-section taken on 99 of FIG- URE 6;

FIGURE 10 is a View in cross-section showing the details of the lowerportion of the pin shown in FIGURE 6 while in operative position in thelower plate of FIG- URES 3 and 4;

FIGURE 11 shows a modified form of extrusion pin;

FIGURE 11(a) is a view in cross-section along line 1IaI1a of FIGURE 11;

FIGURE 12 shows an additional form of modified extrusion pin; and

FIGURE 12(a) is a view in cross-section along line IZa-IZa of FIGURE 12.

It can be seen from the drawings that top plate I of the spinneretadapted to receive the filter pack (not shown), has a central chamber 2and an annular chamber 3 separated from each other by wall 4. In thebottom of chamber 2 are a plurality of holes 5 passing downwardlythrough plate 1 and diverging outwardly from each other. Holes 5 leadinto shallow annular groove 6 formed in the top surface of lower plate 7which, in assembling the spinneret, is fastened to plate 1 as describedbelow. Holes 8 lead from the bottom of annular chamher 3 Verticallydownward through plate 1 and terminate at groove 6 of the lower plate 7.Pins 9, provided with longitudinal passages 10 therethrough arepositioned in holes 8 with a press fit (and may be further fastened inplace by a spline or other means for insuring a tight fit, if desired)with the upper ends of pins 9 extending above the bottom of annularchamber 3 as shown. The press fit of pins 9 may be supplemented by theaction of circular serrations 11 provided at the top of pins 9 to gripthe inside of holes 8.

Pins 9 are circular in cross-section in the portion 12 in contact withholes 8, as shown in FIGURE 7, having a diameter sulficient to give apress fit in holes 8, pins 9 in the major portion 13 passing throughplate 7, having a cross-section which is partly arcuate (as shown at 13)but which has, as by cutting the pin to form chords in the cross-sectionof the pins, the general shape of a mutilated triangle as shown inFIGURE 8. Pin 9 then tapers at 14 near its lower part to a smaller,partially arcuate (as shown at I4) but generally mutilated triangularcross-section as shown in FIGURE 9, the next lower portion of pins 9being necked down at 15 (to form an annular groove) and terminating in ashort annular cylindrical section 16 somewhat larger in diameter thanneck portion 15 as shown in FIGURES 6 and 10, with the ends of pins 9being flush with the outer face of plate 7 and with holes 1.0terminating in orifices 17. Plate 7 is formed with holes 18 passingthrough plate 7, holes 18, which are tapered at their lower ends, havinga circular cross-section throughout equal in diameter to the arcuateportions of sections 13 and 14 of pins 9 to insure a tight fit betweenthe contacting surfaces.

It will be noted that annular orifice 19 is formed at the outer surfaceof plate 7 by the clearance between orifice 18 of the plate 7 and theouter and smaller cylindrical portion 16 of pin 9. The total area of theouter endof orifice 18 (inclusive of orifice 17 and the annularcylindrical portion 16 of pin 9) is collectively referred to as theextrusion orifice designated as 20 in the drawings.

Plates 1 and 7 are fastened with threaded bolts 21 passing through holes22 in plate 7 with the bolt heads being recived in counterbore 23 andabutting at their inner surface the shoulder of counterbore 23, bolts 21being fastened into corresponding threaded holes 24 in plate 11.. Afterthe plates 1 and 7 are assembled and fastened in place by bolts 21,proper alignment is assured by insertion of tapered pins 25 of roundcross-section having a drive-fit into tapered holes 26 of plate 7 andregistering tapered holes 27 of plate 1, the ends of pins 25 being drawninto position above and clear of the outer surface of plate 7.

Gaskets 28 and 29 are inserted in plate 7 prior to assembling thespinneret and are pressed in place as shown respectively into circulargrooves 30 and 31 (gasket 28 being additionally pressed into acorresponding circular groove 32 in plate 1) when plates 1 and 7 arefastened together so as to prevent leakage of the polymer fluid, metalor gas between the plates.

The apparatus is connected with suitable piping and filter packs (notshown) as required to supply a molten polymer and a gas to thespinneret.

In the melt-spinning processes preferred in the practice of thisinvention, a gas, preferably a gas which is inert towards thefiber-forming polymer, flows from annular chamber 3 through longitudinalpassages 10 of pins 9 and out of the spinneret to form the center of thefilament. Molten polymer flows from central chamber 2 through holes intoannular groove 6 (through which pins 9 pass) downwardly through thepassages in plate 7 formed by the clearance between the pin (at itsnonarcuate periphery) and hole 18 of plate 7 (shown clearly in FIGUREwhich represents pin 9 in plate 7 tumed from its position in FIGURE 6 inorder to show the clearance between pin 9 and plate 7), then along thegroove formed at neck and outwardly as a sheath through annulus 19.

It is, of course, understood that the design of apparatus is capable ofconsiderable variation. Thus pins 9, instead of being non-circular incross-section within plate '7, may be circular in cross-section withsufficient clearance being provided between the pins 9 and holes 18 topermit passage of the polymer around the pins 9 as a sheath. Such a formof pin is shown in FIGURES 11 and 11(a). This modified pin has a taperof fii-inch per foot, is approximately of an inch long in the taperbeginning at the bottom of back plate 1 and extending to the spinningorifice. A further form of pin is illustrated in FIGURES 12 and 12(a) inwhich the pin is essentially circular in cross-section diminishing atits lower end as in FIGURES 6 and 10, except that the section of the pinfrom the bottom of back plate 1 to the groove 15 is cut on a chord so asto provide clearance between the pin and spinneret plate 7, therebypermitting fiber-forming polymer to pass from annular groove 6 to thespinneret orifice; this is adapted to give an eccentric feed of polymerso that the hollow filament will be uneven in cross-section for theproduction of inherent- 1y crimpable filaments. V

In the examples, the relative viscosity (7 i.e., the viscosity of asolution of polymer relative to that of the solvent is used as themeasure of the molecular weight. The polyester solutions contained 2.15g. of the polymer in 20 ml. of a 7/10 mixture by weight oftrichlorophenol/ phenol and the viscosity was measured at 25 C.

The following examples in which parts, proportions and percentages areby weight unless otherwise indicated, are intended to illustrate thisinvention and in no manner to limit it.

Example I A spinneret similar to that shown in FIGURES 1 to 10 buthaving 5 spinning orifices, was made having orifices (20) of 0.063 inchin diameter in which the pin 9 had an opening 10 of 0.020 inch and hadan outside diameter of 0.057 inch at the lower edge of the spinneretplate. Moi ten poly(ethylene terephthalate) with a relative viscosity of32 containing 0.3% TiO (as a delusterant) was spun at 280 C. into air atroom temperature and the yarn was wound up at 950 y.p.m. (yards perminute). The pressure on the chamber 3 was controlled by means of asuitable bleed-off system and reducing valves (not shown) from a tank ofnitrogen so as to have a gauge pressure of about 13.5 mm. of water. Thehollow asspun filaments has an inside diameter/outside diameter ratio of0.70 which corresponds to about 50% by volume of void and were ofuniform cross-section throughout their length. The yarn was drawn 200%(to 3 times undrawn length) on a drawing pin maintained at 83 C. Thedrawn yarn had a denier per filament of 3.3, a tenacity of 3.6 grams perdenier, a dry elongation of 34% at the break and an initial modu'lus'ofelasticity of 65 grams per denier. Two worsted fabrics of similarconstruction were woven respectively from yarn made from staple fiberscut from these hollow poly(ethylene terephthalate) continuous filamentsand yarn made from staple fibers cut from solid continuous poly(ethyleneterephthalate) filaments of the same denier. The fabrics were mountedfiat on a board and submitted to the abrading action of a cellulosesponge that revolved in contact with the fabric at a selected, uniformspeed on an axis perpendicular to the fabric surface. After 15 minutessponging, the fabric containing hollow filaments showed only 6.4 pillsper square inch as compared to 33 pills per square inch on the controlfabric. By pills is meant the small balls of fibers that collect on thesurface of a wool-like fabric. The superior resistance to pilling of afabric made from the hollow filaments was quite surprising.

In a second spin, using the same equipment and polymers as before, butwith the nitrogen pressure reduced to a gauge pressure of 6 mm. ofwater, continuous filaments having an inside diameter/outside diameterratio of 0.5 (which corresponds to a hollow space of about 25% of thefilament volume), were made and subsequently drawn 220% on a draw pinmaintained at 83 C. as before, to obtain a strong, yet bulky, yarn.

By increasing the gas pressure above 13.5 mm. of water (gauge),satisfactory spinning was obtained and yarns made having an insidediameter/outside diameter ratio of 0.86 (about 75% hollow space).

Example 11 A spinneret similar to that shown in FIGURES 1 to 10 buthaving 12 spinneret orifices, was constructed with the pin 7 having ahollow passage 10 of 0.006 inch in diameter and a lower outside diameterof 0.030 inch. The orifices 20 of the spinneret had a diameter of 0.034inch. Poly(ethylene terephthalate) of relative viscosity 32 wasmelt-spun from this spinneret at 288 C. using a nitrogengas gaugepressure of 24 mm. of water and the hollow filaments were wound up at1,000 yards per minute. The yarn was drawn 160% over a draw pinmaintained at C. The resulting filaments contained 50% by volume ofhollow spaces, and had a denier per filament of 1.8. A'yarn of solidfilaments of the same polyester was spun and drawn under similarconditions for comparison. given below:

Physical properties of the filaments are It was. quite surprising that alower draw ratio could be used to obtain equivalent tenacity and initialmodulus with the hollow filament as compared to a solid filament of thesame polymer.

The continuous hollow filaments and control solid filaments describedabove in this example were cut into staple length and spun into aworsted-count yarn and fabrics woven therefrom. After weaving andfinishing under similar conditions, the hollow filament fabric had agreater covering power (15% more cover per unit weight of fiber) thanthe control fabric. The pilling tendency of the fabric containing hollowfilaments was about /3 that of the fabric made from the solid filamentsin this construciton. Sweaters knitted from the staple made from thehollow filaments made as described above in this example were softer,more luxurious and weighed 40% less than sweaters with the same coveringpower made from the staple fiber cut from the solid continuous filamentsof the polyester.

The spin of this example was repeated, but the gas pressure reduced toabout 10 mm. (gauge) of water so as to provide a final drawn yarn having10% gas space by volume. A worsted-type fabric was Woven from yarns spunfrom staple cut from these continuous filaments similar to that above.The fabric from the 10% gas-containing filaments had cover equivalent tothat of a solid fiber fabric but weighed 15.5% less. However, the fabricdid not exhibit the resistance to pilling possessed by fabrics made fromthe 50% gas hollow filaamcnts.

A bundle of 50% gas-containing hollow filaments made as above in thisexample were immersed in a 2% dispersion of the dye Artisil Direct Blue(PR 62) in ace tone. After air drying, the filaments were colored mediumblue and showed no tendency toward crocking in rubbing off of the dye.When solid filaments of the same polymer were treated in the dye bath,they were stained only a light blue and the dried filaments crookedbadly.

In a similar manner, the hollow filaments of this example, dyed with thevat dye indigo Violet exhibited freedom from crocking.

Example III A skein of drawn hollow poly(ethylene terephthalate)filaments as prepared in Example I was cut into short lengths with asharp razor blade. The staple fiber thus prepared was covered with asolution of cellulose acetate in acetone. After one minute, the solutionwas decanted, the fiber rinsed twice with acetone and the fiberair-dried. Examination of the dried fiber under microscope revealed thatthe hollow ends of all the fibers were completely sealed by a plug ofcellulose acetate, although the individual filaments were not stucktogether. The product had an actual density of about 0.7gram/centimeters (cubic centimeters) with an apparent density in looselycompacted form of about 0.01 gram/centimeters and floated on waterindefinitely without losing its buoyancy. The product is thus a goodsubstitute for kapok fiber for use in lifebelts and like articles.

A similar product was obtained by cutting a tow of continuous hollowfilaments witha fiyin knife staple curter that had a dull blade. Thepressure of the cutting effectively sealed the ends of the staple.

The thermoplasticity of melt-spun filaments can also be utilized inpreparing the permanently-buoyant, low density staple of this example.In order to prevent adhesion between adjacent filaments, a finishcontaining an aqueous dispersion of a silicone should be applied to thetow of hollow filaments. After drying, the tow is cut by a revolvingknife staple cutter that is heated to approximately the fiber meltingpoint and purposely kept somewhat dull. Temperatures below the meltingpoint down to room temperature have been effective also, presumably dueto the heat generated on impact.

A novel product is made by subjecting staple cut from hollow filament(about 40% voids) of poly(ethylene terephthalate) to a pressure of about10,000 p.s.i. in a bale crimping cylinder. Partial but random collapseof the hollow spaces occurs so that the fiber bulk is decreased but thefibers display a softer hand in fabric than the uncompressed ones. Theuse of a stufier box crimper affords a more regular and controlledintermittent collapse of hollow filament structures at sufficiently highpressures.

Novel effects may be produced by pulsating the flow of gas forming thehollow core thereby varying the thickness and diameter of the filamentwall so as to give filaments similar to the thick and thin solidfilaments made by prior art processes. In this modification thepulsation will normally be so controlled as to maintain continuity ofthe gas core during spinning.

The following example illustrates the making of potentially crimpableand crimped hollow filaments in accordance with the present invention.

spinneret plate, is shaped with section 14 being reduced in diameter ascompared with portion of pin 9 above the spinneret plate, and with thesame reduced crosssection down to the neck portion 15. Section 14 of pin9 is out throughout its length on a chord plane as shown in FIGURES 12and 12(a) of the drawings thereby providing passage for the moltenpolymer through the spinneret plate lengthwise of section 14 down togroove 15 in pin 9. Poly(ethylene terephthalate) having a relativeviscosity of 36 was melt-spun at 280 C. into air at room temperaturetogether with nitrogen (through passage 10 of pin 9) at the gas pressureof Example I with conditions adjusted to give 50% gas-containingfilaments, and the yarn was wound up at 3,000 yards per minute. Withoutfurther processing the yarn was strong and bulky having much the sameproperties as the 50% gas space yarns of Example I. It differed from theyarn of Example I in that the filament wall thickness varied more orless uniformly with the maximum wall thickness being about twice thewall thickness of the filament section diametrically opposite. Thisvarying wall thickness resulted from the design of pin 9 described abovewhich effected the feed of more polymer to one side of the spinneretorifice 20 than to the other.

On exposure to boiling water, free of tension, the yarn became tightlycoiled with each filament taking on a helical configuration, and (asdetermined by microscopic inspection) with the heavy-walled region ofthe filament being toward the inner side of the coils. This coiled orcrimped yarn showed a high degree of stretchiness when made into knittedfabrics and significant bulkiness in woven fabrics of suitableconstruction.

The crimped fibers of this Example 1V can be subjected to a pressure inthe neighborhood of 10,000 pounds per square inch with a piston-cylindertype of press into which a mass of yarn is fed, and random partialcollapse of the hollow spaces in the filaments will occur withinteresting application to conversion into textile fabric havingpleasing novel optical effects and fabric hand and feel. It ispreferable, in this application of the invention, to have a gas-polymerratio in the fila- '2? ments such that the hollow spaces will be 40% orless of the volume of the filament so as to resist too much collapse ofthe filaments under the applied pressure. with higher pressures, e.g.,40,000 pounds per square inch, collapse of the hollow filaments isalmost total with the imparting of a cotton-like random ribbon-like formto the filament which is also useful to produce novel effects whenprocessed into fabric.

While hot water has been mentioned in the above Example IV as ashrinking agent to develop crimp, other shrinking agents may be used toefiect crimping.

The following example illustrates how the same equipment described abovemay be used in forming composite filaments comprising a fiber-formingpolymer as a sheath together with a metal core.

Example V A six-hole spinneret similar to that shown in FIGURES 1 to ofthe drawings having extrusion orifices with an outside diameter of 0.035inch and end 15 of center tubes 9 having an outside diameter of 0.029inch and an inside diameter for orifice 17 of 0.004 inch was made.Fob/(ethylene terephthalate) of relative viscosity 32 was melt-spun as asheath around a molten core of an alloy comprising bismuth, and 60% tinhaving a melting range of 138170 C. The spinneret head was maintained at288 C. and the composite filaments were spun into air at roomtemperature (75 F.) at 500 yards per minute. The as-spun filaments hadan outside diameter of approximately 0.006 inch with a uniform metalcore 'of about 00043 inch in diameter. 'The core occupied about 50% ofthe filamentary volume. The ends of the metal core of a two foot lengthof the as-spun yarn were slivered to facilitate making connections andelectrical measurements made. The yarn had a resistance of 100 ohms perfoot and carried a current of 0.10 ampere for an indefinite period oftime without causing any change in appearance of the polymeric sheath ormaking the composite filament hot. Under a current of 0.125 ampere themetallic core fused apart. This yarn, as spun, was drawn 100% in a 125C. oil bath by hand to give a strong filament with a continuous metalcore having an average diameter of about 0.003 inch completelysurrounded by a uniform polyester sheath. The as-spun filaments couldnot be drawn at room temperature since the core broke at a lowelongation and the sheath soon after. However, a filament prepared in asimilar manner but with about 28% core could be drawn at roomtemperature 150%. The core fractured into segments. A filament with anoriented sheath and. a similarly segmented core was also made by colddrawing a similar filament with a 33% core.

it will be understood that filaments having the fractured core of theabove example present interesting and useful decorative effects in thecomposite filaments and fabrics made therefrom.

Materials used in accordance with the above example may be any metalthat is molten at a temperature at which the polymer for the sheath isstable. Such metals include tin, lead, bismuth, lithium, selenium andtheir alloys with each other and such metals as an antimony and zinc asfor example, bismuth solder, battery plate, white metal, aluminum solderand eutectic alloy, toname a few.

The hollow extrusion pins in the spinneret of this invention may bevaried in exterior and interior size as desired. For filaments ofregular cross-section, the hollow pins are, by virtue of the novelspinneret design, readily centered in the spinning orifices. However,they may be positioned off-center in the spinning orifices so as to givefilament walls of varying thickness to produce filaments which mayreadily be crimped on exposure to boiling water, free of tension, as inExample IV.

Although this invention has been illustrated with filaments having around cross-section, it will be obvious to thoseslg'illed in the artthat the spinneret can be modified within the realm of this invention tospin various crosssections, whether or not the products made have hollowcores or solid cores. By modifying the shape of the orifice (20),cruciform, square, and triangular cross-section shaped filaments may bespun. Such filaments have the advantages of round hollow filaments butconfer a different hand to fabrics made therefrom.

The shape of the hololwor solid core itself can be modified by changingthe shape of passage 10 at the tip of pin 9. Round fibershavingnon-round voids such as oval, triangular, square or star-shaped may bemade. The latter two modifications can be combined to give non-roundfilaments having non-round voids.

In making hollow filaments as above described, the gas pressure ispreferably slightly above atmospheric pressure so as to prevent collapseof the filament at the spinning orifice. The gas pressure at theorifice'may be suitably controlled so as to permit partial shrinkage ofthe spinning polymer on solidification beyond the spinneret orifice. Inaddition to preventing the inherent shrinkage of the polymer onsolidification of the hollow filaments, the air pressure may be lessenedslightly to permit partial collapse or retraction of the tubularfilament. This can be done by proper control of the air pressure inchamber 3 or by suitable design of hole through pin 9. It is preferredthat the air pressure in chamber 3 be not greatly in excess ofatmospheric pressure, e.g., not more than about 30 mm. gage waterpressure.

The hollow products described above in the practice of this inventionare of great advantage in textile applications They confer greaterwarmth and covering power than solid filaments at equivalent weights andconfer a different and, for some applications, a more desirable hand tofabrics made therefrom. Those filaments containing more than 10% hollowspace by volume are particularly valuable in that, when made intoworsted-type fabric, they have a significantly lower tendency to pillthan fabrics of solid filaments.

Hollow fibers otter a route to many new and useful products. All mannerof substances, in a solution or as a melt, can be used to fill thehollow space or coat the inner wall of the filaments by treating thefilaments in a vacuum chamber and then releasing the vacuum. Anonabrasive, but delustered filament, can be made by placing a pigmentin the core, e.g., by filling with a solution of BaCl and then treatingthe filament with sulfuric acid;

this product is opaque to X-rays. Novel effects are obtained by placingluminescent or fluorescent materials in the hollow core. Silver or goldmirrors can be deposited on the walls of the hollow space. Substancessuch as a halomethylated phosphate as shown in US. 2,686,769, and likematerials can be placed in the hollow core to render the filamentsflame-proof. In all the above-mentioned applications, the addedsubstances are protected by the outer layers of the polymer and, hence,are retained in the filament through rough usage.

The spinneret of this invention can also be used to produce compositefilaments of which at least one component is fiber-forming, the othercomponent preferably, thoughnot necessarily, being fiber-forming. Thismay be done by extruding a core material in liquid form through thehollow pins.

The invention is preferably use in the melt-spinning of polymers such aspolyesters and polyamides. However, the spinneret may also be used forthe spinning of filaments composed in whole or in part of cellulosicfiberforming materials, or synthetic addition polymers such asacrylonitrile polymers, either by wet or dry spinning processes.

Because-of their commercialavailability, ease of processing andexcellent properties, the condensation polymers and copolymers, e.g.,polyamides, polysulfonamides and polyesters and, particularly those thatcan be readily melt-spun are preferred in the practice of thisinvention. Suitable polymers can be'found, for instance, among thefiber-forming polyamides and polyesters which are described, e.g., inUS. Patents 2,071,250; 2,071,253; 2,130,523; 2,130,948; 2,190,770;2,465,319 and in other places. The preferred group of polyamidescomprises such polymers as poly(hexamethyleneadipamide), poly-(hexamethylene sebacamide), poly(epsiloncaproamide) and the copolymersthereof. It will be understood from the above description, however, thatpolyesters, because of the resistance to pilling characteristic ofpolyester fabrics comprising hollow filaments, are preferred for hollowfilament production. Among the polyesters that may be mentioned, besidespoly(ethylene terephthalate), are the corresponding copolymerscontaining combined therein, in addition to the terephthalate radical,other acid radicals such as sebacic acid, adipic acid, isophthalic acid,as well as copolymers containing recurring units derived from glycolswith more than two carbons in the chain. Other polyesters are thosehomopolymers derived from the above-mentioned acids and glycols.

The spinneret of this invention is of advantage in that it is of a verysimple construction, is readily maintained, readily permits spinning ofthe various types of filaments referred to herein, permits the accuratepositioning of the hollow or solid core in the filaments for theproduction of filaments uniform along their length, and may easily becleaned.

The invention is particularly applicable to the making of filaments (andof yarns comprising said filaments, whether continuous filaments orstaple fibers) having deniers of the magnitude used in textiles, e.g., adenier per filament in the range of l to (inclusive) and a yarn denierof 30 to 8,000 (inclusive). The filaments may be made into knitted orwoven textiles either unblend;d or blended with other synthetic ornatural fibers. Blending may be effected during the manufacture of theyarn, e.g., by blending wool with staple fibers of filaments spun inaccordance with the invention, or by combining yarns of the filamentsmade by this invention with yarns composed of other fibers.

Any variation from the above description of the invention which conformsto the spirit of the invention, is also intended to be included withinthe claims.

I claim:

1. An improved spinneret plate assembly for producing filaments of afirst given organic composition, said filaments having an annulartransverse cross section and provided with an interior portioncontaining a second given composition of matter, said spinneret plateassembly comprising a housing unit, the structure of said housing unitconstructed and arranged to define a first chamber for the first givenorganic composition and a second chamber spaced therefrom for the secondgiven composition, the structure of said housing unit further definingopenings into each of said chambers for supply of said organiccompositions into the respective chambers, the structure of said housingunit further defining a spinneret face, a plurality of passageways, oneend of each passageway intersecting one of said chambers and the otherend of each passageway intersecting the spinneret face to form apinrality of extrusion orifices, said passageways provided,

adjacent the spinneret face with radially inwardly extending portionsforming restrictions in each of said passageways, each of saidpassageways containing a pin element, said pin element having a firstportion closely fitted and frictionally secured in said passagewayadjacent the intersection with said one of said chambers, and a secondportion extending along said passageway into the vicinity of saidextrusion orifices in the spinneret face, said second portion of saidpin element provided with exterior shoulder means positioned in abuttingengagement against the said radially inwardly extending restrictedportion of said passageway, the frictional fit of the first portion ofsaid pin elements and the engagement of the shoulder means of the secondportion or" said pin elements with the restricted portions of saidpassageways serving to positively align and secure said pin elements attwo spaced points along their lengths in a desired position with respectto said extrusion orifices, the structure of each of said pin elementshaving cut away portions provided in the exterior of the pin element toform channels extending from a position intermediate the pin elementends to the end of the pin element adjacent the extrusion orifice, thestructure of said housing unit further defining a plurality of conduitsconnecting the other of said chambers with each of the channels formedin each of said pin elements so that the composition in said otherchamber may pass through the conduits in the housing unit and throughthe channels along the exterior of the pin elements to the extrusionorifices, each of said pin elements provided with a longitudinallyextending interior passageway connecting the end of said pin element insaid passageway adjacent said one or" said chambers with the end of saidpin element in the vicinity of said extrusion orifice so that thecomposition in said one chamber may pass through the interior passagewayin said pin element to the extrusion orifice concurrently with thepassage of the composition in said other chamber to said extrusionorifices.

2. The improved assembly of claim 1 in which the said shoulder means onsaid pin elements comprises circumferentially spaced segmentalabutment's contacting the re- I stricted portion of said passageways inat least three circumferential points to provide a centering action forthe pin elements with respect to the extrusion orifices.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Rayon and Melliand Textile Monthly,

February 1936 (pages 52 (92) and 53 (93) relied on).

UNITED STATES PATENT ()F F ICE CERTIFICATION OF CORRECTION Patent Noe$014 23? December 26 1961 Alvin Le Breen It is hereby certified thaterror appears in the above numbered pet- I ent requiring correction andthat the said Letters Patent should read as corrected below.

Column 5 lines 73 and 74 for "*curter" read cutter column 8 line 8 for'hololw read hollow line 63 for "use" read used column 9 line 33 for'unblend d" read unblended e Signed and sealed this 24th day of April1962:,

(SEAL) Attestz- ESTON c, JOHNSON DAVID L, :LADD Attesting OfficerCommissioner of Patents

